Actuated valve assemblies are in common use in a variety of industrial applications for the control of the rate of flow of fluid mediums such as steam, water, or other fluids. For purposes of this disclosure, an actuated valve assembly generally will consist of an actuator operatively connected to a valve stem for driving the valve stem, to move a valve element (for example, a gate or plug) within a valve chamber to open and close a valve port. In general, actuated valve assemblies fall within two basic categories which include rising stem valves where the valve stem is axially drawn into and out of the valve body through a gland seal, and rotary or quarter-turn valves where the valve stem is rotated approximately 90.degree. to open or close the value by positioning a rotatable disk or ball having a flow opening formed therein. Rising stem valves further include "rising, non-rotating-stem valves" where the stem is moved axially without rotation, and "rising, rotating-stem valves" where the valve stem is raised and lowered through a rotary or screw type motion.
With respect to the actuation of such actuated valve assemblies, there are two general types of actuated valve assemblies, including: (i) motor-operated valves ("MOV's") which utilize the electric or hydraulic torque motor to turn a worm on a worm gear, turning a rotating drive sleeve that drives either a power screw or a gearbox input shaft, for driving or powering a valve stem and connected valve element; and (ii) pressure-operated pneumatic or hydraulic actuators (mostly air operated valves or "AOV's") in which a fluid pressure acting on a diaphragm or piston, and often opposed by a spring, provides a linear force for moving a rising stem valve or operating a drive which moves a rotary or quarter-turn valve.
Examples of MOV's include rising, non-rotating-stem valve assemblies and rising, rotating-stem valve assemblies and rotary or quarter-turn valve assemblies.
Examples of AOV's include rising, non-rotating-stem valve assemblies, and rotary or quarter-turn valve assemblies.
Currently, it is known to include monitoring systems or devices within the valve bodies or housings of conventional actuated valve assemblies for monitoring and evaluating axial and torsional forces being exerted upon the valve during the operation of the valve to provide an indication of the performance of the valve assembly.
There are monitoring instruments, both temporarily and permanently installable, primarily available for motor-operated valves such as Limitorque-driven units such as are found in nuclear power plants. Such devices are shown in patents typically classified in U.S. patent class 73, subclass 168, and an example of which are shown in U.S. Pat. Nos. 4,787,245 and 5,469,737. Additionally, U.S. Pat. No. 5,090,239 teaches a valve sensing instrument mounted within grooves or cutouts formed along the exterior sidewall of the valve stem, typically just above the packing of the valve assembly.
One problem that appears to still exist with known measured valve assemblies is, however, the exposure of the valve sensors or monitoring instruments to the environment of the valve where such sensors are subject to damage and environmental influence.
Accordingly, a need exists for an actuated valve assembly having a system for monitoring and evaluating the forces acting on the valve stem or shaft that can operate efficiently despite the environmental conditions within the valve assembly and which is easy and economical to manufacture and can easily be installed as a replacement for existing load.